Method for producing trialkyl lead fluoroborates

ABSTRACT

A NEW METHOD FOR PREPARING TRIALKYL LEAD FLUOROBORATES.

States Patent ABSTRACT OF THE DISCLOSURE borates.

This application is a continuation of my copending apfiled sepnzs 1971 now 4;, trialkyl lead fluoroborate catalyst. Secondly, this inven- Pat. No. 3,725,447. p

I INTRODUCTION This invention relates to the redistribution of the alkyl radicals in tetra alkyl lead compounds. More specifically,

A new methodfor preparing trialkyl lead fluoro- :1.

this invention relates to the redistribution of tetra methyl lead and tetra ethyl lead by use of a trialkyl lead fluoroborate catalyst.

This redistribution process between alkyl lead radicals is well known to the art and may be carried out in the presence of various catalysts. The redistribution of organic groups between two diiferent tetra alkyl lead compounds occurs in a random manner to produce a statistical distribution of all five possible tetraorgano lead derivatives based on the relative concentration of the two alkyl lead compounds. This reaction can be described by the following equation:

where R and R are different straight or branched chain alkyl radicals.

A catalyst is required to effect the redistribution reaction between tetraorgano lead compounds. Etiective catalysts are Lewis acid compounds such as zinc chloride, zinc fluoride, mercury (II) chloride boron trifluoride, aluminum chloride, aluminum bromide, and dimethyl aluminum chloride as well as zirconium (IV) chloride, tin (IV) chloride and triethyl lead chloride, triethyl lead iodide, phosphorous trichloride, arsenic trichloride, bismuth trichloride, iron (III) chloride, and platinum (IV) chloride. Activated alumina and other metal oxides are also effective redistribution catalysts.

The redistribution reaction and catalysts therefore are described in greater detail in 62 JACS (1940), pp. 1099- 1104 and in the volume Organic Compounds of Lead by Shapiro and Frey, published by John Wiley and Sons, 1968. While a number of catalysts are mentioned in these two references as well as in several US. patents, including 2,270,108 and 3,151,141 all seem to be unsatisfactory for various reasons one of which is the lack of thermal stability. Also, these catalysts often form undesirable side products and require a water wash subsequent to the reaction. In the present invention the use of the trialkyl lead fluoroborate catalysts prevents the formation of these side products thereby eliminating the need for water washing. It further has been discovered that the use of a trialkyl lead fluoroborate catalyst in the redistribution reaction of tetra alkyl radicals results in a rapid reaction with little, if any, thermal instability of the catalyst being observed.

3,804,872 Patented Apr. 16, 1974 OBJECTS i 2 C] out unwanted sideeifects.

A further object is to provide a trialkyl lead fluoroborate catalyst to redistribute the alkyl radicals in a tetra alkyl lead compound.

A still further object is to provide a method of making trialkyl lead fiuoroborates.

THE INVENTION This invention involves the redistribution of alkyl radicals in tetra alkyl lead compounds by the use of a tion involves a method of making trialkyl lead fluoroborate. Generally, the trialkyl lead fluoroborate catalyst is dissolved in water in a concentration of approximately by weight; other concentrations ranging from 50 to 75 by weight also may be employed. The aqueous solution of the trialkyl lead :fluoroborate is added to the tetraalkyl lead mixture, such that the concentration of catalyst is from 10 to 50% based on the weight of alkyl lead mixture. The preferred concentration is from 20 to 33% by weight. The redistribution occurs rapidly at ambient temperature and pressure. No external heating or cooling is necessary and there is no thermal instability of the tetra alkyl lead mixture or the catalyst.

The reaction should be conducted with good agitation. The reaction is complete within from 1 to 8 hours dependent upon the efliciency of the mixing technique used. While room temperature is preferred, other temperatures ranging from 40 F. up to about F. may be used although no advantage is achieved above or below room temperature.

Typical tetra alkyl lead compounds which may be used in the practice of this invention are tetra methyl lead and tetra ethyl lead.

THE TRIALKYL LEAD FLUOROBORATE Trialkyl lead fiuoroborates may be described by the following formula:

1'11 Ra-PbBF4 where R R and R are straight or branched chain aliphatic hydrocarbons having from 1 to 6 carbon atoms.

The preferred trialkyl lead fluoroborate of this invention is trimethyl lead fluoroborate.

The trialkyl lead fluoroborate is produced by the reaction of a tetra alkyl lead with boroflnoroic acid:

The reaction is conducted by utilizing aqueous solutions of borofiuoric acid to which is added the tetra alkyl lead compound. The concentration of the borofluoric acid solutions may vary from as little as 1% up to its saturation solubility. The reactions are normally conducted at room temperature and are usually completed in from 2 to 3 hours.

The trialkyl lead fiuoroborate solutions produced by the method described above may be concentrated by evaporation of water to produce solutions having concentra tions within the range of from 5 to about 75 by weight.

vention."

To 450 grams of an equal molar mixture of tetra methyl lead and tetra ethyl-lead, 200 grams of a 75% aqueous solution of trimethyl lead fluoroborate is added. The reaction proceeds with stirring at room temperature for four hours. There is no formations of side products and therefore no water wash of the mixture is'needed. Analysis of the redistributed mixture was found to be as follows.

Tetraalkyl lead: Mole percent ..Tetra methyl 5.1 Trimethyl ethyl 23.6 Dimethyl ethyl 42.3

.Methyl triethyl 23.6 Tetra ethyl 5.4

. The following examples are given to}ilhistrz zite the 3; .i

1..,molecule, such as dimethyl diethyl lead,-monothyltriethl lead, etc. The resulting effect is the same as if two difierent alkyl leads were used in proportion, providing the same number of difierent alkyl groups.

EXAMPLE II One hundred fifty grams of tetra methyl lead and grams of 48% borofiuoric acid aqueous solution are add,- ed to a' reaction vessel and stirred two hours at ioor'n temperature at which time the'reaction hasiproceeded. to completion. This product is isolated and then i s ready to be used in the redistribution reaction as described in Example I.

Iclai'm: 1. A method for, producing trialkyl lead fiuoroborates which comprises reactinga tetra alkyl lead with an aqueous solution of borofiuoric acid.

2. A method of producing trimethyl lead fluoroborate which comprises reacting tetra methyl lead'with an aqueous solution of borofiuoric acid.

References Cited Shapiro et al.: The Organic Compounds of Lead, Inter} science PubL, John Wiley & Sons, New York, pp."7781 and 102 (1968). J. Organometal Chem., vol. 6, p. 363 (1966).

HELEN M. S. SNEED, Primary Examiner 

